1985 Cj7 block identification question - JeepForum.com
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post #1 of 4 Old 07-10-2020, 11:04 AM Thread Starter
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1985 Cj7 block identification question

Hi, could someone please decode my block, I’ve gotten a lot of confusing google and forum searches. Thanks in advance
503C29. Jeep has a 4.2L currently in it. A mechanic told me it’s not the correct 85 engine.

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post #2 of 4 Old 07-10-2020, 01:11 PM
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HI From what I see on this site see link.. scroll thru the box to the proper items on that site..


It shows 85 258.. so I don't know what that machanic was talking about unless it had some mods on it..
good luck
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post #3 of 4 Old 07-11-2020, 06:19 AM
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29 March 1985 that engine was tested at the factory and issued out, probably to the production line, It is a 258 with 9.25:1 compression with a 2 barrel carb. That is from the Factory Service Manual. It is not the date the casting was made, which would have been months before.

Engines built up in other countries had different coding, but this looks like a Toledo built engine. In Indonesia they stamped the engine number here to match the frame number, starting with a J and then a serial number.

It could also be a 1970s engine, Toledo reused the engine year codes. However there are signs to look for. In 1980 Toledo changed from the "heavy" engine to the "light" engine so ther are signs to tell you which decade it came from. This is not certain overseas, my 1982 J20 has a "heavy" engine which must have been in stock for some time.

So what else can you tell us about the engine? Does it have a plastic valve cover? does it have an aluminium manifold? Is it covered in hoses and strange looking electronics and vaccum actuators? Any other casting numbers?

To check manifold manufacture date you should see a circle on the top left of the manifold. What does it say?
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1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE
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post #4 of 4 Old 07-11-2020, 08:34 PM
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1981 CJ5 
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Originally Posted by BagusJeep View Post
It could also be a 1970s engine, Toledo reused the engine year codes.
My last jeep was an 81, and the build code had the code for "81'...... and that was great.. until things did not fit right.

Turned out, "81" and "77" used the same code, and I had an 77 engine.

THese days, the heavy and light versions are easiest enough to spot. ie valve cover, dip stick, exhaust... and how much emmisions crap.. lol
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